The present invention relates, in general, to the field of methods and apparatus for implementing hunt group support for a crosspoint controller. More particularly, the present invention relates to a method and apparatus for implementing hunt group support for a crosspoint controller within an Enterprise Systems Connection switch ("ESCON.TM." is a trademark of International Business Machines Corporation).
Current approaches, such as those used in the ESCON Director series of point-to-point switches provide only a single path between any source and destination port. In other words, there is a one-to-one association between an attaching port and the paths to all other ports within the switch. This architecture limits the routing between any two physical ports to one, and only one, path through the switch. As such, the particular path must be available (that is, neither port can be busy) for a connection to be established between the source and destination ports, and a "busy" condition at either the source or destination port will deny the connection from being established and force the requesting device attached to the port to retry the connection request. U.S. Pat. No. 5,107,489 describes a typical ESCON switch and port states in more detail, the disclosure of which is herein incorporated by this reference.
The present ESCON Director configurations utilize a dual-ported 256 bit busy array with the one-to-one relationship of a single busy bit associated with a single port. Busy bits are associated with the physical source/destination port number ("PNUM") and during a connection request, two bits of the busy bit array are accessed, one associated with the source of the connection request ("SRC_PORT") and the other associated with the destination ("DST_PORT"). These bits represent the state of each port, and if a connection can be made, then the busy bits addressed by the source and destination port numbers are updated to reflect the new "busy" condition. The individual ports thereafter return a "clear" pulse to the associated busy bits upon termination of the connection.